The present invention relates to a fan device for an internal combustion engine, and more particularly to a temperature controlled fan device with a braking arrangement.
A temperature controlled fan for an internal combustion engine is well known. A publication "AUTOMOTIVE ENGINEERING VOLUME 4 GASOLINE ENGINE" issued in July 1980 shows such a temperature controlled fan on pages 362 and 363 and in FIGS. 11.85 and 11.86. According to the known temperature controlled fan, a torque of a fan driving shaft is transmitted via an oil to a fan. This fan comprises a fluid coupling, a bimetal and a valve so as to control the amount of oil supplied to the fluid coupling, thus controlling fan speed. The bimetal is exposed to air coming from a radiator and closes the valve at low temperatures to reduce the amount of oil supplied to the fluid coupling thereby reducing the transmitting torque and thus causing the fan to rotate at low speeds or idle. At high temperatures, the bimetal opens the valve to increase the amount of oil supplied to the fluid coupling thereby increasing the transmitting torque and thus increasing the fan speed.
In this known temperature controlled fan device, the fan creeps and does not stop rotating even if the valve is closed by the bimetal because there remains a small amount of torque in the fluid coupling and there exists a friction of a bearing carrying the fan. This leads to a problem that the engine is cooled by cooling air from the fan upon cold start of the engine, leading to a poor warm-up performance. Besides, this worsens the performance of a heater which uses engine coolant.